Historically, a user of one computer system has been able to send a message, such as an electronic mail message, from the computer system to another user who is using another computer system. The sender of the message can use the message to alert the user of the other computer system of the occurrence of some event that the sender wishes to pass on to the receiver of the message.
Computers can also present event notifications to a user of the computer system. For example, if the user receives electronic mail, then the user receives a message box on the display screen of the computer that informs the user that an electronic mail message has been received by the user at the computer.
Paging systems have long been available to inform a user of an event, such as a phone call. For example, if a user of a pager receives a phone call from another person, then the user receives a notification on the user's pager of the phone call, such as a beep or a vibration generated by the pager. The notification may include specific information such as the phone number to use to call back the other person displayed on the visual display of the pager.
Telephony systems have message waiting indicators (MWI) available on some telephony devices that provide notification of an event, such as a voice mail message. For example, a telephone may have a small light that lights up or blinks when a voice mail message was left with the voice mail service for that telephone.
Conventional computer systems are also capable of sending electronic mail messages to a user's computer to inform the computer of the occurrence of an event of interest to the user. For example, a user may subscribe to a computerized stock brokerage service and request that he or she be informed if the price of a specific stock falls (or rises) to a certain level. The service can then send the user an electronic mail message informing the user of the change in the stock price.